The So20,w of unsheared DNA from whole cell lysates of Escherichia Coli

Abstract

We present measurements of the sedimentation coefficients of DNA present in whole cell lysates of E. coli. The method used is a preparative version of the band sedimentation experiment of Bruner and Vinograd. We show that in order to obtain reliable data on the time dependence of sedimentation, it is necessary to accelerate and decelerate the rotor over much longer times than the standard centrifuge allows. We describe the necessary modifications to the preparative centrifuge and use them to determine the So20,W of unsheared E. coli DNA. The value for the fastest moving components in the lysate is 220 S. The molecular weight of the DNA corresponding to this sedimentation coefficient is probably 1.7 X 10(9) g/mole. However, alternative values cannot be ruled out.